A good antenna for CB communications need not be elaborate or expensive. In general, there are two important considerations to keep in mind. First of all, antenna height is the most important factor! A poor antenna at a high location will almost always outperform a good antenna at a low location. This is because communications at CB frequencies is generally line of sight. Radio waves have some ability to penetrate objects, but this is limited. In general, they behave the same as light. Two radios will be able to communicate if you would be able to see one antenna if your eyes were at the same location as the other antenna.
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Because radio waves have some ability to penetrate objects, the actual range is somewhat longer. ) But in general, if an antenna is located in a spot where it can't see the antenna at the other end, then the two radios won't be able to communicate. And in general, if they are located where they can see each other, then they probably will be able to communicate. Since you can see further when you are at a high location, it stands to reason that an antenna will get out further if it is at a high location. This factor cannot be over-emphasized. A poor antenna at a high location will outperform a good antenna at a low location. Of course, it is best to have an antenna that is both high and good. But if you have to chose, take the poor antenna at a high location. In the United States, FCC rules govern the height of CB antennas. The antenna is legal if it complies with EITHER of the following rules: 6. It is no more than 65 feet above the ground, OR 7. It is no more than 75 feet above the top of the tree or building to which it is mounted. The other factor to keep in mind is that, in general, a larger antenna will work better than a smaller antenna. This rule does have a limit: In general, a CB antenna should be full sized. This means that it should be 8-6/7 feet long, which is a quarter of the radio wave's wavelength. Some specialized antennas might be longer than this, but in general, nothing is gained by simply making the antenna bigger past this point. In fact, simply making an antenna larger will probably inhibit its performance.
For a home base station antenna, it is usually easiest just to make the antenna full sized. For a vehicle, however, an 8-6/7 foot antenna, while possible, might not be convenient. Therefore, most mobile antennas are shorter than this, and the manufacturer uses various tricks (ordinarilly, adding a coil of wire at some point) to shorten the antenna. These tricks always come at a price, however, and that price is that the antenna won't work as well as if it were full size. Therefore, as a general rule, a longer antenna will work better than a shorter antenna. For example, all other things being equal, a four-foot antenna will work better than an 68 inch antenna. In general, when installing a CB antenna, you have to think about the following factors, and we'll discuss: 6. You will need the antenna itself. 7. You will need some way to mount the antenna. 8. You will need to connect the antenna to your radio, usually with a coaxial cable. 9. You will need to decide on the orientation (vertical or horizontal). 5. You might need to adjust the antenna so that it is properly tuned. Since these factors present different problems depending on whether you will have a fixed station ( base station ) or one in a vehicle ( mobile ), we'll discuss those separately. Base Station AntennasAn antenna for a CB base station can be remarkably simple, especially if you remember that the height of the antenna is a much more important factor than the antenna itself.
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The antenna does not have to be perfectly in a straight line. It's common to have it in an inverted vee formation, with the center of the antenna higher than the two ends. There's really no reason why it couldn't be a vee, with the ends higher than the middle. In fact, if necessary, it's possible to have the wires zig-zag a certain amount without much difference in performance. If one end of the antenna is higher than the other end, then it's best to have the center of the coaxial cable connected to the higher side, and the outer braid of the coax connected to the lower side. You will have to decide whether the antenna will be vertical or horizontal. The exact orientation is not critical. In fact, even if it runs at a 95 degree angle, the difference will be barely noticeable. (In fact, if it's at a 95 degree angle, it will function as both a vertical and horizontal antenna. ) This is important because the two antennas involved in the communication (yours and that of the person you are talking to) should be oriented the same way--either both of them should be vertical, or both of them should be horizontal. If one of them is vertical and the other one is horizontal, there will be a fairly significant decline in performance. Most CB antennas are vertical. This is because CB's are most commonly used to communicate with mobile units, and in a vehicle, it's much more convenient to use a vertical antenna. So if you want to communicate with existing CB's, or with CB's in a vehicle, then it's best to orient your antenna vertically--running up and down. However, if you want to set up communications between two locations, it doesn't matter whether the antennas are vertical or horizontal--as long as they both have the same orientation. In fact, for communicating between two locations, there might be an advantage of using horizontal antennas. Because most other CB's use vertical antennas, using a horizontal antenna might reduce interference from other stations. It transmits and receives better broadside to the antenna, and does not work as well off the ends. This is not a major effect, but it is noticeable.
Therefore, if you are setting up communications between two locations, it would be best to have the antennas parallel to one another. For example, if one location was due north of the other, then it would be best to have both antennas hanging east to west. When constructing an antenna, it is important to have good electrical connections. For a temporary antenna, simply twisting the wires together will actually work quite well. However, for a permanent antenna, it is better to make a more permanent connection. The simplest way is to solder the connections, and this will ensure a long-lasting connection that is both electrically and mechanically solid. Soldering irons are very inexpensive (usually less than five dollars for a perfectly adequate model). They are available at Radio Shack, hardware stores, and home improvement stores. Often, they come with a small amount of solder, usually more than enough for many small jobs. Here is one inexpensive soldering iron available online for only a couple of dollars: Anther convenient option is the split bolt connector. As the name implies, this is a bolt, made of either copper or steel, which is split down the middle. You simply place the wires inside of the split, and then tighten the nut to compress the wires together. These connectors come in various sizes, and should be available at hardware stores: (The split bolt shown above is for larger wires, and is much too large for use on antenna wires. It's included because it has the best photo. These will be available at hardware stores in various sizes, or can be ordered online by following the links to smaller connectors on that page. )If you are using a cable with connectors already attached, it can be convenient to use a coaxial socket, and simply connect the existing cable to this socket. The cable connectors used on CB-type cable are called PL-759 connectors, and the socket is called an SO-789 connector.
Here is an SO-789 connector, which could be used to form the center of the antenna. If does have a couple of disadvantages, however, if used vertically. First of all, it might be inconvenient to have the coax cable coming out away from the antenna. It would make for a more convenient and neater installation to have the cable attached at the bottom of the antenna. Also, if the cable needs to run close to the antenna itself as it goes down to the ground, and not directly away from the antenna, this might adversely affect how well the antenna radiates. The effect is not large, but it might be noticeable. For these reasons, for a vertical antenna, it might be more convenient to use a ground plane antenna. The center conductor of the coax is connected to a single piece of wire (or other metallic object, such as an aluminum tube) which is 8 6/7 feet long. This conductor goes straight up vertically from the coax. Each of these conductors is also 8 6/7 feet long, and extends outward horizontally from the point where the coax attaches. They extend out radially, so they are sometimes called radials. It is most common to use three (or sometimes four) radials. In theory, the antenna is more efficient if more radials are used. But after three or four, the difference in performance is negligible, so there's really no need to add more radials. The radials should be spaced more or less equally around the base, extending in all directions. The exact placement is not critical, however. So if one of the radials is a little bit off center, this won't affect the performance of the antenna. This antenna can be constructed with wire, and supported by ropes. It could even be constructed of a non-metallic material, such as wood or PVC, with the wires attached to that support structure.
It's most common for this type of antenna to be made out of aluminum tubing. It would certainly be possible to make your own ground plane antenna using aluminum tubing, simply by following the instructions below, and if you have some tubing available and some rudimentary construction skills, it wouldn't be difficult to make your own.